The invention relates to a radio system relaying packet-switched traffic and to a method for connection establishment in a radio system relaying packet-switched traffic. The invention relates particularly to a radio system where terminals have various radio path characteristics.
A significant shortcoming in current radio systems and in those that are being developed is the limited amount of radio resources available. The number of radio frequencies is restricted and they are distributed among various systems and operators. Numerous different solutions have been created to solve this problem.
Previously developed radio systems meant for public use are based on circuit-switched technology. In systems implemented according to this technology, a specific channel is reserved for the connection between the devices involved, the connection being available to the devices for the entire duration of the connection, irrespective of whether there is traffic on the channel all the time or not. This solution has been sufficient for systems relaying primarily speech. However, with increasing telecommunications needs, transmission connections are used for transmitting data. The traffic relayed on data connections is often highly bursty, i.e. at times data is transferred in large amounts and a lot of transmission capacity is needed on the channel, whereas occasionally the traffic load on the channel is low. From the point of view of capacity deployment, packet-switched transmissions are an extremely good solution for these connections. In packet-switched connections, the channel is not allocated to the terminals for the entire duration of the connection, but the channel is only allocated when data needs to be transferred. Consequently, diverse radio systems employing packet-switched service have been developed, at least some of the connections between the terminals being established using a packet protocol. Among these systems are GPRS (General Packet Radio System) and its enhanced version EGPRS (Enhanced General Packet Radio System).
Since various data services are available and they have differing data transmission needs, many systems include the possibility to establish connections of varying capacity. Moreover, many systems involve diverse terminals which may be provided with highly varying data transmission properties and capability to deploy the resources of the system. For example, different equipment and data transfer capacity is needed for transferring speech, written communications or video. In addition, there may be devices that can only use specific frequency ranges and others that can utilize all the frequencies reserved for the network. Consequently, when a radio connection is to be established, the system should know the type of the terminal that needs the connection and the data transmission capacity. There are also networks that may have different packet system protocols available, such as the GPRS and EGPRS, and, depending on its characteristics, the terminal can use one or the other.
In prior art solutions a terminal that needs to transmit data in packet format contacts the network and informs that it wishes to establish a connection and, at the same time, it informs what kind of a terminal it is, i.e. the radio path characteristics it has. These characteristics include for example the frequencies the device needs for communication, and the transfer modes of different capacities that the terminal can utilize. A prior art signalling for connection establishment is illustrated in FIG. 1. The Figure shows the essential parts of messages sent by different devices. The messages sent by the network part are marked with DL (downlink). A terminal sends a CR (Channel Request) 100 to the network part of the system. The network part allocates one radio block to the terminal and responds by sending the terminal an IA (Immediate Assignment) 102. The terminal uses the allocated radio block to send a PRR (Packet Resource Request) 104. This request comprises information about the terminal""s radio path characteristics. The network part allocates one or more channels to the terminal and responds by sending a new response 106 where the reserved channels are informed to the terminal. The terminal then starts to send data 108. In the example of FIG. 1, the terminal uses three parallel 110-114 channels.
One of the drawbacks of the above method is that it is not possible to know whether the terminal needs GPRS (General Packet Radio System) or EGPRS (Enhanced General Packet Radio System) resources. Another problem is that one allocated block is sufficient for sending one control message, but one control message is not always enough for relaying the radio characteristics of the terminal. Consequently, a terminal having diversified characteristics does not necessarily receive appropriate resources.
The signalling that takes place before data transmission is a multi-step process, i.e. it comprises a plural number of steps depending on the amount of data to be transferred and the amount resources available. When GPRS is used, the signalling can take place either on a PCCCH (Packet Common Control Channel) or a CCCH (Common Control Channel), but with EGPRS only PCCCH can provide efficient signalling. This causes delay in the transmission of the signal and yet the data transmission is not necessarily carried out in an optimal way due to insufficient signalling capacity.
It is therefore an object of the invention to provide a method and a radio system allowing connections between a terminal and a network to be established smoothly and effectively. This is achieved with a connection establishment method of the invention employed in a radio system relaying packet service, in which method the terminal informs the system network part that it wishes to send data to the network part; the network part receives the message and allocates a default amount of radio resources to the terminal; the network part informs the allocated resources to the terminal; the terminal sends a first control message to inform the network part about the terminal""s radio path characteristics. According to the method of the invention, when the network part allocates the default amount of radio resources to the terminal, it reserves one or more radio blocks for the terminal""s control messages, and when the terminal sends information about its radio path characteristics to the network part, the terminal also informs in the message if there are additional characteristics, and, in that case, the terminal sends a second control message comprising information about the terminal""s radio path characteristics.
The invention also relates to a radio system relaying packet-switched traffic, in which system a terminal is arranged to inform the system network part that it wishes to send data to the network part; a network part is arranged to receive the message and to allocate a default amount of radio resources to the terminal; the network part is arranged to inform the allocated resources to the terminal; the terminal is arranged to send a first control message to inform the terminal""s radio path characteristics to the network part. According to the system of the invention, when the network part allocates the default number of radio resources to the terminal, the network part is arranged to reserve one or more radio blocks for the terminal""s control messages, and when the terminal informs the network part about its radio path characteristics, the terminal is arranged to inform in the message if there are additional characteristics, and, in that case, the terminal is then arranged to send a second control message comprising information about the terminal""s radio path characteristics.
According to a preferred embodiment of the invention, after having received the information about the allocated resources from the network part, the terminal starts to send data to the network part, immediately after it has sent the requested control messages using the allocated radio resources.
In another preferred embodiment of the invention, the terminal is allocated a predetermined number of channels immediately after the first channel request. Data transmission can then begin, and, when it begins, the terminal""s characteristics are signalled to the network. According to another preferred embodiment of the invention, the network part is arranged to allocate radio resources to the terminal in accordance with the terminal""s characteristics, which allows the number of channels to be increased, when necessary.
According to a further preferred embodiment of the invention, the first control message comprises information about the terminal""s radio path characteristics preferably with regard to the frequency band the network part first inquired about in the control message it sent. The second control message sent by the terminal informs the terminal""s radio path characteristics preferably with regard to all frequency bands available in the network. If there are so many radio path characteristics that they cannot be included even in this message, then new control messages are sent until all the radio path characteristics have been informed within the scope of the allocated resources.
The method and arrangement of the invention provide several advantages. Data transmission can be rapidly initiated and channel deployment becomes more efficient. On the other hand, the network is informed more effectively than before about the terminal""s characteristics, which allows an appropriate number of channels to be allocated for a connection. Furthermore, the terminal can be used for sending more information to the network than before, i.e. information from all frequency bands supported by the network and the terminal. Previously the information has been limited to one frequency band alone.